Flexible strip lighting apparatus and methods

ABSTRACT

The present invention is directed to the use of light emitting diode (LED) lighting in flexible strips, where the color of the lighting emitted from the flexible strip is consequential to the encapsulation process and heat from the lights is adequately dissipated.

The present application claims priority to U.S. Provisional PatentApplication No. 61/897,448, filed on Oct. 30, 2013, and incorporatedherein by reference.

BACKGROUND OF THE PRESENT INVENTION

Certain types of lighting emit light, such as white light, in aparticular color temperature. White light may be characterized in termsof temperature. Color temperatures over 5,000K are considered coolcolors, meaning they emit light in a bluish-white range, whereas lowercolor temperatures (typically 2,200-3,000K) are considered warm colors(emitting light in a yellowish white through red range). Currently withLEDs, if the color goes below 2,700K, the emitted light is amber, whichdoes not provide for the preferred color in typical residential andcommercial applications. At present there is a desire to emit light inthe warm range with LEDs which themselves emit light at below 2,700K.

In addition, the present invention is directed to meeting a desire tohave light emitted preferably by LEDs encased in flexible strips. Suchflexible strip lighting can be used in a variety of applications, suchas but not limited to commercial displays, under cabinets, cove/soffit,and for safety purposes (such as aisle lighting). Flexible strips permiteasy installation and avoid the need to deal with stringing andinterconnecting the lights and the flexible strips allow suchinterconnection to be in place in advance, freeing the installer (orde-installer) to lay strips instead of individual lights.

This strip lighting is particularly desirable in commercial settings,where lights are installed and uninstalled frequently, particularly indisplays which have short installation durations and the need to installis under time pressures.

In many of these circumstances, the color of the light is particularlyimportant. For example, under cabinet lighting in certain commercialenvironments needs to be bright white, whereas cove/soffit lightingmight need to be warmer color temperatures. Such flexible strips canpotentially satisfy these color and installation needs, so long as thecolor of the LEDs can be adjusted from flexible strip to flexible stripin the production process.

Currently the main and only way to effect color temperature of LEDs iseither via phosphor directly placed on the LED chip or via remotephosphor layers that are used as lenses over blue LEDs. Such a devicemay not be cost effective to manufacture. Another issue with the remotephosphor is aesthetics; when the light is off, it appears bright yellowor orange depending on the color temperature of the fixture.

Prior to the present invention, the use of LED flexible strips has beenlimited to the color temperature offered by the LED chip andincorporating remote phosphor solutions is both impractical mechanicallyspeaking as well as cost prohibitive. The costs accrue from manufactureof the strips, the costs associated with the need to dissipate heat fromthe strips, and the costs to assemble and install the strips. In short,the present invention includes a novel approach so as to make theassembly of such devices more readily usable and economic in commercialenvironments.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention is directed to the use of light emitting diode(LED) lighting and particularly to the use of lights in flexible strips,where the color of the lighting emitted from the flexible strip isconsequential to the encapsulation process and heat from the lights isadequately dissipated. Although the present invention is primarilyfocused on flexible linear LED lighting, it is also applicable to otherLED lighting formats, such as but not limited to low voltage lightingand other such lighting and in other non-linear or non-flexible strips.The present invention is further directed to connectorization of thestrips (or other form of encapsulated lights) and to a cutting tool forsizing strips for installation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 displays a top-down view of an encapsulated LED strip.

FIG. 2 depicts the strip of FIG. 1 in a bottom-up view.

FIG. 3 depicts one view of the connector of the present invention.

FIG. 4 depicts an alternate view of the connector of the presentinvention.

FIG. 5 depicts yet another alternate view of the connector of thepresent invention.

FIG. 6 depicts a view of the connector bracket of the present invention.

FIG. 7 depicts a rendering of the cutting tool of the present invention.

DESCRIPTION OF THE PRESENT INVENTION

The present invention is directed to various attributes of product andmethod of producing product, including attributes of flexible linear LEDlighting, where those attributes include placing LEDs on flexible PCB,adjusting the color emitted through the an elastomeric encapsulationthat encapsulates the LEDs, dissipating heat of the encapsulated LEDsand circuitry, connectorizing the encapsulated strips, and a tool forcutting the light-emitting strips. One objective is to mimic the warmthof the traditional incandescent lamp using LEDs of other wavelengthsand/or emitting at lower power. Another objective is to use higherintensity LEDs and dissipate heat more effectively than in priordesigns.

Color Adjustment

The present invention includes a new method to adjust the color, colortemperature, color rendering index (CRI) and the different R factorsthat influence the color rendering of the projected light. This isachieved in part by using combinations of various silicone dyes(preferably non-phosphor based). This is a cost effective and moreaesthetically pleasing solution than prior solutions, particularly whenthe fixture/light source is visible to the end user.

With regard to adjusting the R factors, the present invention permitsadjustment of the R factor from R1-R8 (color rendering index or CRIvalues) as well as R9-R14 values. CRI is an industry rating system thatmeasures the accuracy of how well a light source reproduces the color ofan illuminated object. Test colors R1-R8 are pastel-like and R9+ aremore vivid.

The present invention is further directed, in part, to pigmentation ofan elastomer. Such elastomers may be any of silicones, polyurethanes,thermoplastics such as poly(methyl methacrylate) (“PMMA”) or anothersimilar elastomer (referred to herein collectively as “silicone”). Thesilicone pigmentation results in an apparent clear strip, but with theability to change the color of the emitted light of the encapsulatedLEDs (or other light source) to a more desirable color. The pigmentationelement may be added in various concentrations comprising one or morepigments (such as but not limited to yellow, red, or brown), which aredistributed uniformly through the silicone. The lights themselves arealso distributed, typically uniformly, and encapsulated in the silicone,together with a printed circuit board (PCB) and end connectors. Theresult is a flexible strip with embedded LEDs which emits light at acolor temperature different from the actual LED's color temperature. Thestrips are attachable to one another.

The preferred pigments used are SILc pig silicone based, althoughalternate pigments may be used so long as the pigments distributeuniformly in silicone.

For example, the present invention can use 2,700K LEDs and produceproduct that emits light at a discrete, pre-determined point within an1,800K-5,000K temperature range. In this example, the basic formula is a1:20 ratio between red and yellow, and the ratio is adjusted in varyingconcentrations to achieve different values in the range noted above. Themore concentrated, the closer the color is to 2,200K. For a bottom endof the range (2,200K-2,400K), brown pigment may be added to the red andyellow mixture above at 1:20 ratio. In the preferred embodiment, oncethe pigmentation is added to the silicone, the composition is maintainedin a liquid form in a linear mold, with lights and PCB laid in thesilicone as desired, and the silicone with pigmentation is allowed toharden. The mixtures noted above are mixed into the silicone anddispensed over the LED strip that is sitting inside a silicone tray.This process fully encapsulates the LEDs.

Note that the process may result in various shades and colors, dependingupon the pigments and quantities used. Lights can appear white, yellow,red, and green, among others.

In another example, the LEDs (or other lights) can be inserted withlensing to direct the lighting if desired.

Encapsulation

The present invention is also directed to encapsulating LED lighting ina flexible strip. FIG. 1 shows a top-down view of the encapsulatedsilicone strip 100 of the present invention, including the pre-selectedLEDs 106. FIG. 2 shows a bottom-up view. These views show a completefirst strip 102 attached to a second strip 104 and, particularly, thetwo strips 102 and 104 are commonly encapsulated.

In the preferred embodiment of the present invention Sorta clear 40 isused as the encapsulating silicone, which is a platinum, or “addition”,cured silicone. Alternatively, tin, or “condensation”, cured siliconemay be used. Platinum-cured is preferred because it is longer lastingwithout becoming brittle, does not shrink and is more durable in variousenvironmental conditions, such as changes in temperature or in thepresence of other chemicals.

In the present invention, strips of LED-mounted PCBs (“boards”) areattached to one another to form a potentially lengthy chain and may becommonly or separately encapsulated in silicone (or some othercomparable encapsulator which allows for light from LEDs to filterthrough). Each strip 102 and 104 is nominally six inches long, althoughthe length of a strip may vary based on application of use. Each strip102 and 104 is preferably the same length (other than end strips, whichmay be cut to fit), although different length strips may alternativelybe used.

At each end of the strip, or at regular intervals in the strip,connectors 108 are used for connecting sections or strips. FIGS. 3-5show views of the preferred embodiment of the physical connector of thepresent invention. A connector 302 at one end mates with a connector 402at the end of the adjoining strip. A PCB 306 is embedded within a strip,and runs from connector to connector. That is, a connector attaches toeach end of the PCB 306, all encapsulated within a strip, other than theexposed ends of the connectors.

The net result is a linear LED strip encompassing color-changingcharacteristics for internal lighting.

PCBs

In the preferred embodiment, a PCB runs the length of the strip. Likethe strip, the PCB is flexible. Each PCB has an upper surface and alower surface. LEDs are mounted on the upper surface, preferably atequally spaced intervals. Also, other electrical elements, such as butnot limited to a resistor and a current regulator, are also mountedalong the PCB.

FIG. 3 shows a cross-section cut of the encapsulated silicone strip 100of the present invention, including lighting and connector.

The PCB 306 has two layers/levels. Each consists of at least two traces304 used to run 24 VDC through the fixture. One layer is the general onethat goes through an entire potentially 22 foot run (44 boards in total)and the top layer is used for distributing the power for each individualcircuit (every 6 inch board with 6 LEDs, 1 resistor and 1 currentregulator). As opposed to present solutions, which only utilize the‘real estate’ covered by the footprint of the LED and its immediatesurrounding portion of the PCB 306 for cooling, the present inventionutilizes the entirety of the PCB traces 304 to dissipate heat. In otherwords, the present invention, utilizes the copper that runs through thelength of the PCB 306 to dissipate the heat.

The PCB 306 itself is made of FR4 material (fiberglass composite with anepoxy resin binder) sandwiched by two layers of copper.

Following mounting of the elements, including connectors, the flexiblePCB 306 is encapsulated in silicone.

Importantly, in other embodiments, the strip need not be linear orflexible but could take various other shapes or forms. For example, apartially circular strip might be beneficial for some applications. Inaddition, the hardness of the silicone can vary by introducingquantities of a hardening agent to the silicone.

Encapsulation is accomplished by placing the PCB 306 in a siliconechannel/extrusion 308 and the channel is filled with silicone 310. Oncecured, the PCB 306 adheres to the silicone material that makes up thechannel and thereby fully encapsulates the PCB 306.

Heat Dissipation

In addition to encapsulating the lights and changing color, the presentinvention addresses the need to dissipate heat from the encapsulatedlights. In the preferred embodiment, heat dissipation is achieved boththrough properties of the encapsulating silicone as well as through theinternal PCBs, although in other embodiments, one or the other might beused alone.

In the preferred embodiment, the silicone is formed of two distinctlayers where one layer, in this embodiment the lower layer, allows forimproved heat dissipation and the upper layer and sides may not. In thisembodiment, the silicone used in the lower portion might be more porousor might have improved heat dissipating qualities and, consequently, thesilicone-based material in the upper portion might be somewhat differentthan that of the lower portion. Also, by having two different types ofsilicone serving to sandwich an LED flexible strip, manufacture can besimpler. That is, the lower portion may be extruded, the LED flexiblestrip laid on top, and the upper portion formed thereafter and formed toadhere to the lower portion.

A further advantage of use of heat dissipative silicone is to safelyencapsulate higher wattage/output products while managing the heatdissipation. That is, because heat may be dissipated through the design,higher watt and therefore more intense lighting can be used. The heatdissipation ability needs to be matched to the embedded wattage.

Alternatively, to achieve this goal, the silicone used may include heatdissipative properties, either in the silicone itself, how the siliconeis hardened, or the addition of added materials in the siliconecomposition. In the preferred embodiment, the silicone itself providesfor dissipation of heat through the bottom portion.

Alternatively, the heat dissipative material is incorporated in the baseof the LED circuitry, which is also fully encapsulated in silicone. Inthe preferred embodiment, the PCB and, more particularly, the copper inthe PCB is used for heat dissipative purposes, and both sides of the PCBare utilized.

Because of the unique nature of the material—silicone plus one or morepigments and heat dissipative capability—the co-extruding and assemblyprocesses are unique as is the application of use. The extruding processis unique in lighting because the process requires two differentextrusion materials to be coextruded and bonded, so that at the end ofthe extrusion process the result is one piece made up of 2 bondedmaterials.

Connectorization

The usual way of connecting flexible strips in installations involvessoldering wires together. Such an approach is labor intensive andexpensive. While AVX connectors have been used for connecting strips ofLED lighting, the present invention makes use of them on a flex board.That is, the connectors are mounted on a flexible board to facilitatebetter electrical connectivity than in previous designs. FIGS. 4 and 5show the male connector 402 and female connector 302, respectively, ofthe invention. Further, the connectors 302 and 402 may be connected toone another and encapsulated.

For such use, the present invention includes a new and improved bracket(made of high density polyethylene, or HDPE) which provides a benefit ofpreventing board to board disconnect. That is, the flexible strips maybe extruded in defined lengths and, in implementation, may be connectedelectrically with AVX connectors, and help in place more securelymechanically using the aforementioned bracket. The brackets arephysically connected to the end connectors and form a solid connectionbetween flexible strips. The need for this bracket arises due to theflexible nature of our product and the fashion it is handled in thefield. These connectors are designed to be used on rigid and noneaccessible circuitry. We are using them in a very different method. SeeFIG. 6 for a detailed drawing of the connector bracket 600 of thepresent invention, including nominal dimensions. As shown, the connectorbracket 600 is a rectangular bracket that is 10.5 millimeters by 11millimeters in size, has a cutout in the center of the bracket that is5.8 millimeters by 8 millimeters in size, has corners with a radius of0.7 millimeters, and a triangular cutout along the top and bottom sidesof the bracket that are 0.5 millimeters deep. Of course, dimensions mayvary based on application.

Cutting Tool

In addition, because lengths of use vary, it is important to easily andrapidly cut lengths of the flexible stripping so as to conform to theneeds of the implementation. As a result, the present invention includesa new and improved cutting tool to allow for quick and easy disconnectat any given connector point on the LED flexible strip. This cuttingtool facilitates easy cutting in the field to desired lengths (based onstrips nominally being six inch increments) as well as preparing eitherend of the cut lengths to be reconnected to an extension/jumper cable.The tool of the present invention is a hinged cutting tool made of HDPEand includes a cutting template (using metal blades) to match theconnectors on the PCB.

The tool of the present invention also has an additional purpose ofscoring the silicone layer above the connector itself to allow for easyremoval. This scoring is needed to allow a good mechanical connectionwith the locking mechanism of the connectors on any given end of anextension cable. See FIG. 7 for a cutting tool 700 for reference.

The invention claimed is:
 1. An apparatus for strip lighting comprising:a first printed circuit board (PCB) formed as a linear strip, a secondPCB formed as a linear strip, a plurality of light emitting diodes(LEDs) mounted on one side of the first and second PCBs, a matableconnecting device comprising a first connector mounted on the first PCBand a second connector mounted on the second PCB that is different fromthe first connector, a bracket configured to secure the first connectorto the second connector, and a pigmented elastomer commonlyencapsulating the first and second PCBs including the matable connectingdevice and the bracket; wherein a pigment in said pigmented elastomeralters at least one of the color and R factor of the visible lightemitted from said LEDs.
 2. The apparatus of claim 1 wherein at least onepigment used in said pigmented elastomer is introduced to said elastomeras a dye.
 3. The apparatus of claim 1 wherein said apparatus for striplighting is surface mountable.
 4. The apparatus of claim 1 wherein saidelastomer is absent of silicone.
 5. The apparatus of claim 1 whereinsaid LEDs are rated in the 1,800-5,000K color range.
 6. The apparatus ofclaim 1 wherein said elastomer is distributed so as to allow forcomparatively greater heat dissipation from one side than the other. 7.The apparatus of claim 1 wherein said heat dissipative capability of theelastomer on one side of said first and second PCBs is distinct fromheat dissipative capabilities of the elastomer used on the other side ofsaid first and second PCBs.
 8. The apparatus of claim 1 wherein saidfirst and second PCBs are flexible.
 9. The apparatus of claim 1 whereinthe first connector is a male connector and the second connector is afemale connector configured to receive the male connector.
 10. Theapparatus of claim 9 further comprising a cutting tool comprising ahinge and a cutting template configured to match the matable connectingdevice.
 11. A method for formulating strip lighting comprising the stepsof: formulating a plurality of printed circuit boards (PCBs) comprisinga first PCB and a second PCB, each in the form of a strip; mounting aplurality of LED devices on one side of each of the first and secondPCBs; mounting a first connector on the first PCB; mounting a secondconnector on the second PCB that is different from the first connector;coupling the first PCB to the second PCB at least in part by attachingthe first connector to the second connector and securing the firstconnector to the second connector using a retaining bracket; andcommonly encapsulating the first and second PCBs including the firstconnector, the second connector, and the retaining bracket in pigmentedsilicone comprising a pigment.
 12. The method of claim 11 wherein saidelastomer comprises a plurality of parallel layers with differing heatdissipation properties in at least two layers.
 13. The method of claim12 wherein said elastomer in at least one of said parallel layersincludes an improvement in the ability to dissipate heat from saidprinted circuit board over that of at least one other layer.
 14. Themethod of claim 13 wherein said layer with the improved heat dissipativeproperties is in a layer away from the mounted LEDs.
 15. The method ofclaim 11 wherein at least one pigment used in said pigmented elastomeris introduced to said elastomer as a dye.
 16. The method of claim 11wherein said lighting apparatus is surface mountable.
 17. The method ofclaim 11 wherein said elastomer is absent any silicone.
 18. The methodof claim 11 wherein said encapsulating is such that the resulting devicehas greater heat dissipation from one side than the other.
 19. Themethod of claim 11 wherein the first and second PCBs are flexible.